The concept of Supplemental Downlink was introduced in Long Term Evolution (LTE) Release 9 and is being extended for Release 10 to include up to three additional carriers in unpaired spectrum. The unpaired spectrum is used only for downlink, whereas the paired spectrum is used for both downlink and uplink.
Typically, the paired spectrum and unpaired spectrum is used to carry wireless radio signals, e.g., LTE wireless radio signals. However, there are limitations on the unpaired available spectrum which may be available.
Light Emitting Diodes (LEDs) capable of generating white light are expected to become the dominant source of lighting in the commercial and residential sectors in the future. Recent research has demonstrated that such LEDs can be intensity modulated at a high bandwidth. When combined with the high optical power intensities (tens of Watts) in typical indoor lighting conditions, the high modulation rate offers the potential for broadband wireless data communication in the hundreds of Mbps.
Based on the above discussion, it would be beneficial if this potential capacity of visible light communications (VLC) was utilized. Although it appears that LED lighting, e.g., within a building, is a viable means for adaptation to create a VLC transmission downlink, it may not be commercially practical to try to create a VLC uplink including VLC transmissions from user equipment (UE) devices to an access point, e.g., due to hardware considerations, interference considerations, battery power considerations, cost, etc. One of the key challenges with utilizing Visible Light Communication (VLC), is the absence of an uplink, e.g., a reverse link, corresponding to a VLC downlink. In order to efficiently manage a downlink including traffic data, it is beneficial to have feedback via an uplink, e.g., for communicating signals including acknowledgments.
Based on the above discussion, it would be advantageous if new methods and apparatus were developed to make use of the potentially available VLC downlink in an efficient manner.